Help! Realistic STA-2300 Power level LED problem

[Martin Angus]

Hi to all...this is my first post.

I have the subject receiver that I am putting back into service. I bought it new in 1982 and have had it in storage for the last 17 years. I recently decided to use it again and took it out of the plastic bag. I worked perfectly...almost!

Two issues I want to deal with while I have it apart on the bench for cleaning.

1. When I powered it up after 17 years in a bag, the 4 lamps worked. The 2nd time I powered it up (hours later) all four bulbs failed. I have 8.6 volts going to the bulbs. What are the odds that all four bulbs are toast? Where can I replace them?

2. Several years after buying this receiver, the top row of power level LEDs stopped working. I never bothered having it fixed as it didnt effect performance. The bottom row works great. Top row does not function on low or high power switch. I unscrewed the pcb linked to the LEDs (labeled REALISTIC P-200929) and saw nothing obvious - nothing loose, burned etc. No bad fuses... So, its likely a circuit component? Where should I start?

I don't want to reassemble this brute until these two issues are fixed.

Not sure how to add pics but two can be seem here: https://1drv.ms/f/s!AnpGKCirF_OO5QcuKF2XDvpJP1r7

Thanks in advance

 

[ChrisMarantz]

Do you have a Service Manual?

If the dial lamps are wired in series, if 1 lamp fails they all go out

It looks like your LED's have a driver IC for each row (top and bottom) it could be the driver IC for the top row.

You will definitely need a Service Manual to work on this. - Chris

 

[Binkman]

Greetings and welcome to A.k.

I also own the 2300, original owner. I seriously doubt the lamps failed but more what signal drives them. power left right.
No free service manual can be found but you can buy one at
http://stereomanuals.com/man/rep/radio-shack/index.htm

Note this unit was the first of the digital front ends.. so problematic.
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While you are in the box...........
Only issues I have had (similar pull from storage) was the power switch staying on red (intermittent) and a flakey stereo mono switch. I fixed the power switch issue by soldering a crap load of power supply leads to solder joints mounted on various solder trees and wire wraps. Many were cold or aged and the wrap trees are not gold. I just tacked a 'tad fast melt' of 60/40 kester about 1/4 inch above the base to not over heat the base pcb joint on the wraps. just a tad.

-------- end zone was also the tuning boards became alive for tuning and more responsive all around.
-------- I have not replaced one capacitor in the entire amp. mind you I have not over driven the unit. (got complaints from the neighbors but more inquiries to where is the party? )
---
Back to the flake stereo mono switch. it simply failed to revert from one to the other.. I had to position it to determine one or the other mode so I disconnected it and it remains in assembled in 'stereo'. All those front switches are identical but note cannot be cleaned nor taken apart. As a matter of fact, I tried it and the switch fell apart. The parts are so small I can't imagine re-assembling one.

Your power switch may be flakey, too or has failed. But note my resoldering.. may be linked to that preamp board? The soldering pics you post look fine to the led board. perhaps a component that drives these.

will amend this thread. (I do have a replacement board for my use and leaves three good switches but I need to pull the old board.)
bink

edit point.. you can't expect this amp to be instant on.. these battleships just for a warm up period require many minutes at no input. The start up shut down procedure is make sure all pots and switches are in neutral and volume off, all buttons out = off and put the selector switch to Aux with nothing hooked up that for testing. I used the Aux for another tuner and that made no difference as the Aux is sort of a safe start zone and for diagnostics. I don't have the orig. manual but that was deemed proper start/shut down. I don't have any issues following the owners instructions for same for all these years.

 

[OMGCat!]

The upper row of the LEDs not working sounds like a bad solder joint somewhere. Tap around with a chopstick or something non conductive while it's playing and see if they come back to life. Once you locate the problem area go over the solder joints and you should be set.
For the other issue I'd start by checking the bulbs for continuity to see where to start your troubleshooting. It's not likely they would all go bad at the same time but they are all the same age and have the same amount of hours so it's not impossible either.
If it's not the bulbs then get your chopstick back out and start poking around the boards where the bulbs get their power. See if you can get them to flicker on and off. If so then touch up those joints as well.

 

[Martin Angus]

First off, thanks to all who replied to my request for help. As it turns out, the issues are both solder joint related in the same circuit board. Tap tap...and the upper (left) power level lights came on. I almost cried...I hadnt seen them lit up since about 1984. ;-) And after a few more taps, one of the four lamps lit up...so maybe 3 are blown or else I need to tap some more. This entire circuit board is going to get solder touch ups. I think I like it here at AudioKarma!

 

[Binkman]

certainly good news Martin;

I would not continue to run the amp until you do the resoldering those led's may come alive, my leds work fine and didn't touch that board but after opening up the bottom panel I could easily see many questionable joints so I just hit everything as noted on trees and the wire posts. quite a few were obvious poor work. everything wired got a touch up and I gave it a idle time on/ off to let the caps reform. low volume on the speakers etc. exercise the pots, play with the tuner.. plug in stuff. Also note that the pots are 'clickable' and don't need deoxit. just rotate if you hear some scratchyness' selector switch might need a shot mine didn't need it. cleaned rca jacks you know general cleanup use only mild dish soap mix for the face plate. Note the dial face trim is plastic!
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These are great receivers and amps. Dont mess with tuner just dust out. I used have mine on a rotational antenna and on a good cold night I could easily get (from raleigh nc) chicago on a skip, toronto, montreal, nyc etc. Also after my cleanup I found mounting a dipole vertical instead of horz. pulled in stations much better.